photon

noun

pho·​ton ˈfō-ˌtän 

1

: a quantum of electromagnetic radiation

Should a substance happen to have a lot of electrons in a higher level, and a lower level is mostly empty …, then a photon can cause an electron to transfer from a higher state to a lower one. This change releases energy and creates a new photon, in addition to the one which caused the transfer. This photon can in turn induce more electrons to fall to a lower state.

—Robert Gilmore

2

dated : troland

photonic

fō-ˈtä-nik 

adjective

Did you know?

Science and the Photon

It was Albert Einstein who first theorized that the energy in a light beam exists in small bits or particles, and scientists today know that light sometimes behaves like a wave (somewhat like sound or water) and sometimes like a stream of particles. The energies of photons range from high-energy gamma rays and X-rays down to low-energy infrared and radio waves, though all travel at the same speed. The amazing power of lasers is the result of a concentration of photons that have been made to travel together in order to hit their target at the same time.

Examples of photon in a Sentence

Recent Examples on the Web

The simulated black hole's event horizon is about 16 million miles wide, and viewers will see a large flat cloud of hot gas and glowing structures called photon rings. —Kerry Breen, CBS News, 7 May 2024

Cloud structures called photon rings and a flat, swirling cloud of hot, glowing gas called an accretion disk surrounding the black hole serve as a visual reference during the fall. —Eric Lagatta, USA TODAY, 7 May 2024

Solar sails run on photons from the Sun, causing small bursts of momentum that propel the spacecraft farther away from the star. —Passant Rabie / Gizmodo, Quartz, 2 May 2024

Paradoxically, this reluctance to interact is also the main disadvantage of photons. —The Physics Arxiv Blog, Discover Magazine, 30 Apr. 2024

In their gaseous phase, many natural and man-made molecules, including ammonia, carbon monoxide, hydrogen sulfide, and methanol, absorb photons when stimulated at terahertz frequencies, and those absorption bands can serve as chemical fingerprints. —IEEE Spectrum, 7 Mar. 2024

At that time, the entire universe was younger than the Earth is now; our planet only started to coalesce after the Mothra photons had reached the halfway mark in their cosmic journey to a world that would develop a giant infrared-sensitive space telescope just in time to catch their light. —Joshua Sokol, Quanta Magazine, 29 Aug. 2023

The collision would have kicked off a chain of particle decay that ended with the production of photons, electron-positron pairs and neutrinos. —Stephanie Pappas, Scientific American, 20 July 2023

According to theory, the particles that carry that force — bosons — should be massless, like the photon that transmits light. —Dennis Overbye, New York Times, 9 Apr. 2024

Word History

Etymology

phot- + -on entry 2

First Known Use

1916, in the meaning defined at sense 2

Kids Definition

photon

noun

pho·​ton ˈfō-ˌtän 

: a tiny particle or bundle of electromagnetic radiation

Medical Definition

photon

noun

pho·​ton ˈfō-ˌtän 

1

: a unit of intensity of light at the retina equal to the illumination received per square millimeter of a pupillary area from a surface having a brightness of one candela per square meter

called also troland

2

: a quantum of electromagnetic radiation